This invention relates to packaging materials, and more particularly to an improved packaging material which, upon being disposed, will degrade over a relatively brief period of time upon being exposed to the elements--i.e., water, insects, fungi, etc. More particularly this invention relates to a novel process for producing such packaging material.
The extensive use of synthetic plastics for packaging and wrapping materials has caused a proliferation of the environment with refuse which defies disposal short of incineration. Even then, incineration of disposed plastic items tends simply to redistribute the pollution from the earth to the atmosphere. Waste disposal, therefore, has become a national crisis, particularly in the larger metropolitan areas. Unfortunately, the populated areas often seek to solve the waste problem by transporting their waste to the more rural areas, thus generating also social-political problems.
Numerous efforts have been made to combat this problem by developing biodegradable materials which can be substituted in place of the heretofore non-biodegradable plastics so often employed for packaging materials such as wrapping films, shipping boxes, containers, and the like. U.S. Pat. No. 3,921,333, for example, suggests that the problem can be at least partially solved by using synthetic plastic materials which are biodegradable--i.e., thermoplastic polymers which can be degraded by living organisms, usually microorganisms.
The U.S. Pat. No. 4,312,979 discloses various methods for preparing polysaccharides by extracellular cultivation from the genus Pseudonomas in a nutrient medium. Although the patent does not disclose or teach the production of a packaging or wrapping material, it does suggest that polysaccharides can be used as moldable materials for biodegradable films, as well as for other purposes.
Accordingly, one object of this invention is to provide a novel method of producing a biodegradable packaging material from a gellable plant extract, such as for example from a polysaccharide such as agar-agar.
Still a more specific object of this invention is to provide a novel method of producing a biodegradable packaging material by freeze drying a liquid mixture containing a polysaccharide gelling agent.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.